You need not be overly confused about this issue; for it is merely a difference of opinion based on the distinction between what is preferred and what is merely permissible. There is no doubt that the cut off point for consuming suhoor is the arrival of dawn (i.e. fajr time); however, the preferred time for abstention is ten or fifteen minutes earlier than that.
The basis for establishing the preferred time of abstention (imsaak) is an authentic tradition from the Prophet, peace be upon him: For one of his companions narrated the story of taking suhoor with the Prophet, peace be upon him. Upon hearing it, someone asked him, “What was the time gap between your suhoor and fajr salah? he replied, “The time required to read fifty verses of the Qur’an.” It is estimated that this time can be ten or fifteen minutes and not more.
This, therefore, is the basis for the imsaak time you are used to in Turkey; however, it must be pointed out that the above mentioned hadith does not state that it is not permissible to consume suhoor later than that; for it only states that it was the sunnah of the Prophet, peace be upon. As for the permissibility of consuming suhoor until the arrival of dawn, it has been established by the clear text of the Qur’an, “Eat and drink until the white thread of dawn becomes distinct from the black thread of night.” (Qur’an: 2: 187).